Rotating flow control devices having stabilized bearings

ABSTRACT

Rotating flow control diverters and rotating blow our preventers having stabilized bearings. The bearing elements are stabilized in a neutral operational position using coil springs disposed in passages in a shoulder defined on the outer surface of the rotating tubular shaft of the rotating flow control device.

FIELD OF THE INVENTION

The present invention relates to rotating flow control devices, and more particularly to rotating flow control devices having stabilized bearings.

BACKGROUND

In the oil and gas industry it is conventional to mount a rotating blowout preventer or rotating flow control diverter at the top of a blowout preventer (BOP) stack beneath the drilling floor of a drilling rig while drilling for oil or gas. The rotating flow control diverter serves multiple purposes including sealing pipe that is being moved in and out of the wellbore while allowing rotation of same. The rotating flow control diverter may also be used to contain or divert fluids and gases such as drilling mud, hydrocarbon wellbore products, and surface injected gas into a recovery line.

Typically, a rotating flow control diverter consists of rubber strippers or sealing elements and an associated hollow quill that both rotate with the drill string within a robust housing. Rotation of the strippers and the hollow quill within the housing is facilitated by a bearing assembly usually having an inner race that rotates with the drill string and an outer race that remains stationary with the housing. The bearing assembly is isolated from fluids and gases emanating from the wellbore by a series of seals. A rotating blow out preventer consists of the same elements as a rotating flow control diverter provided that in a rotating blow out preventer, the stripping element is subjected to external hydraulic force to seal onto the drill pipe. In a rotating flow control diverter, the stripping element normally seals on the drill pipe by means of a stretch fit system that is augmented by fluid pressure from the wellbore.

Downtime in drilling operations must be minimized to maximize efficiency and productivity. Further, it is imperative that production equipment must be robust and reliable to safeguard workers operating on and about the drill floor. It is therefore desirable that rotating flow control devices be designed with components that function in a trouble free manner, and that are at least substantially as durable as other associated drilling components.

Bearing failure is one of the more prevalent manners in which a rotating flow control device may encounter mechanical problems. A common cause of premature bearing failure in rotating flow control devices is movement or shifting of the bearings during operations resulting is misalignment. Misalignment of the bearings can result in excess bearing loads and friction that can greatly shorten the life of a bearing.

Prior art solutions designed to prevent uncontrolled movement of the bearings during operation of a rotating flow control device are limited. Typically, in practice great time and effort is expended to shim any possible space out of the stacked assembly to ensure the bearings stay in place. However, even after the bearings in a rotating flow control device are carefully shimmed with conventional metal shims, they still have a tendency to move or compress through time as the rotating flow control device is operated, particularly when the rotating flow control device experiences varying loads and temperatures.

Accordingly there is a need for an apparatus and a method that promotes the stability of the bearings of a rotating flow control device. It would be preferable if the apparatus is simple, robust and efficient to use and if it mitigates the problems associated with the prior art solutions.

SUMMARY OF THE INVENTION

In one aspect of the present invention, the invention comprises a rotating flow control device apparatus having stabilized bearing elements, the apparatus comprising;

-   -   (a) a stationary housing having a central bore;     -   (b) a tubular shaft rotatably mounted in the central bore of the         stationary housing, the tubular shaft having an inner surface         and an outer surface, the outer surface of the tubular shaft         defining a shoulder having an upper face and a lower face, the         shoulder defining a plurality of passages extending from the         upper face to the lower face;     -   (c) a coil spring disposed in each passage;     -   (d) a bearing assembly axially and radially supporting the         tubular shaft, the bearing assembly comprising;         -   (i) an outer housing releasably mounted to the stationary             housing, the outer housing and the outer surface of the             tubular shaft defining an annular space between them;         -   (ii) bearing elements disposed in the annular space, the             bearing elements being mounted on the outer surface of the             tubular shaft in a position adjacent to the upper and the             lower faces of the shoulder whereby the coil springs in the             passage are compressed by the bearing elements and exert a             resistive push force on the bearing elements.

In one embodiment, the passages and the tubular shaft are aligned longitudinally. In other embodiment, the apparatus further comprises shims mounted on the outer surface of the tubular shaft adjacent to the bearing elements such that the bearing elements are sandwiched between the shoulder and a shim. In another embodiment, the apparatus further comprises a top cap that releasably attaches to the outer housing of the bearing assembly, the top cap retaining the bearing elements within the annular space and compressing the bearing elements against the springs.

In one embodiment the rotating flow control device is a rotating flow control diverter.

In another embodiment, the rotating flow control device is a rotating blow out preventer.

In a further aspect of the present invention, the invention comprises a rotating flow control device apparatus having a stabilized bearing elements, the apparatus comprising;

-   -   (a) a stationary housing having a central bore;     -   (b) a tubular shaft rotatably mounted in the central bore of the         stationary housing, the tubular shaft having an inner surface         and an outer surface, the outer surface of the tubular shaft         defining a shoulder having an upper face and a lower face, the         shoulder defining a plurality of pockets recessed into the upper         face and the lower face;     -   (c) a coil spring disposed in each pocket;     -   (d) a bearing assembly axially and radially supporting the         tubular shaft, the bearing assembly comprising;         -   (i) an outer housing releasably mounted to the stationary             housing, the outer housing and the outer surface of the             tubular shaft defining an annular space between them;         -   (ii) bearing elements disposed in the annular space, the             bearing elements being mounted on the outer surface of the             tubular shaft in a position adjacent to the upper and the             lower faces of the shoulder whereby the coil springs in the             pockets are compressed by the bearing elements and exert a             resistive push force on the bearing elements.

In one embodiment, the pockets and the tubular shaft are aligned longitudinally. In other embodiment, the apparatus further comprises shims mounted on the outer surface of the tubular shaft adjacent to the bearing elements such that the bearing elements are sandwiched between the shoulder and a shim. In another embodiment, the apparatus further comprises a top cap that releasably attaches to the outer housing of the bearing assembly, the top cap retaining the bearing elements within the annular space and compressing the bearing elements against the springs. In one embodiment, the pockets are only defined in one of the faces of the shoulder and a single bearing element is mounted on the outer surface of the tubular shaft adjacent to such face.

In a further aspect of the invention, the invention comprises a method of stabilizing bearing elements in a bearing assembly of a rotating flow control device, the bearing assembly comprising an outer housing, the bearing elements and a rotatable tubular shaft having an outer surface, the tubular shaft being disposed within the outer housing and being supported axially and radially by the bearing elements, the method comprising;

-   -   (a) defining a shoulder having an upper face and a lower face on         the outer surface of the tubular shaft;     -   (b) defining a plurality of passages through the shoulder         extending from the upper face to the lower face;     -   (c) inserting a coil spring into each passage; and     -   (d) mounting the bearing elements on the outer surface of the         tubular shaft in a position adjacent to the upper and lower         faces of the shoulder such that the coil springs in the passages         are compressed and exert a resistive push force on the bearing         elements.

In one embodiment of the method, the passages and the tubular shaft are aligned longitudinally. In another embodiment, the method further comprises the step of securing a top cap to the outer housing to retain the bearing elements and to compress the bearing elements against the coil springs. In one embodiment of the method, the rotating flow control device is a rotating flow control diverter. In one embodiment of the method, the rotating flow control device is a rotating blow out preventer.

In one embodiment of the method, instead of defining passages in the shoulder, pockets are defined in the upper face and the lower face of the shoulder and coil springs are inserted into each such pocket. In a further embodiment of the method, pockets are only defined in one of the faces of the shoulder.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like elements are assigned like reference numerals. The drawings are not necessarily to scale, with the emphasis instead placed upon the principles of the present invention. Additionally, each of the embodiments depicted are but one of a number of possible arrangements utilizing the fundamental concepts of the present invention. The drawings are briefly described as follows:

FIG. 1 is an elevated diagrammatic depiction of one embodiment of a rotary flow control diverter.

FIG. 2 is an elevated diagrammatic depiction of the tubular shaft of one embodiment of the present invention.

FIG. 3 is an exploded diagrammatic view of one embodiment of the present invention showing how it inserts into the outer housing of a bearing assembly of a rotary flow control device.

FIG. 4 is a diagrammatic depiction of the springs in the passages of one embodiment of the present invention.

FIG. 5 is a diagrammatic depiction of the springs in the pockets of one embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention relates to an apparatus for stabilizing the bearings in the bearing assembly of a rotating flow control diverter. When describing the present invention, all terms not defined herein have their common art-recognized meanings. To the extent that the following description is of a specific embodiment or a particular use of the invention, it is intended to be illustrative only, and not limiting of the claimed invention. The following description is intended to cover all alternatives, modifications and equivalents that are included in the spirit and scope of the invention, as defined in the appended claims.

A rotating flow control diverter generally comprises a stationary housing adapted for incorporation into a wellhead and a rotating quill portion adapted to establish a seal to a tubular such as tubing or drill pipe that is passed through the quill. The quill is rotatably and axially supported by an internal rotating assembly comprising bearings and a seal assembly for isolating the bearings from well fluids.

FIG. 1 depicts one embodiment of a rotating flow control diverter (10) that forms the subject of co-pending PCT Application CA 2011/000668, owned by the Applicant. As can be seen in FIG. 1, the rotating flow control diverter (10) comprises a stationary housing (14) adapted at a lower end by a flange connection (16), to operatively connect with a wellhead or blow out preventer (not shown). In operation for diverting and recovering fluids and gases from the wellbore, the stationary housing (14) can be fit with one or more outlets along a side portion of the housing (14) for the selective discharge of well fluids and gases.

The stationary housing (14) has a bore (28) for receiving fluid and gas from the wellbore. The rotating flow control diverter (10) has a sealed bearing assembly (15) having an axially rotatable inner tubular shaft (12) disposed therein. The inner tubular shaft (12) has an elastomeric stripper element (18) supported at a downhole end of the inner tubular shaft (12).

The bearing assembly (15) has a robust outer housing (22). The outer housing (22) and the inner tubular shaft (12) form an annular space disposed in which is a sealed fluid chamber (24). The sealed fluid chamber (24) is enclosed by the outer housing (22), the inner tubular shaft (12) and an upper cap (26) and a lower seal (20) The upper cap (26) is attached to outer housing (22) using set screws (19) or such other suitable attachment means as would be selected by one skilled in the art. The sealed fluid chamber (24) contains bearing elements (not shown) and lubricating fluid (not shown) for lubricating the bearing elements. It can be understood from FIG. 1 that the bearing elements disposed in the sealed fluid chamber (24) radially and axially support the inner tubular shaft (12).

One skilled in the art will appreciate that a rotating blow out preventer is comprised of the same elements as a rotating flow control diverter. The difference between the two pieces of equipment is that in a rotating blow out preventer, the stripping element is subjected to external hydraulic force to seal onto the drill pipe while the stripping element in a rotating flow control diverter typically seals on the drill pipe by means of a stretch fit system. The Figures and the following description of the invention will be described in the context of a rotating flow control diverter, but it should be understood that the invention described herein may be utilized in the same manner in a rotating blow out preventer. The term “rotating flow control device” as used herein shall include both a rotating flow control diverter and a rotating blow out preventer.

FIG. 2 depicts a modified inner tubular shaft (40) of the apparatus of the present invention for use in rotating flow control devices to support, stabilize and centralize the multiple encased bearings. As will be described in more detail, when installed, the inner tubular shaft (40) preloads the bearing elements (30) with an external push force created by the compression multiple coil springs (46). The inner tubular shaft (40) has an inner surface (46) and an outer surface (48), the outer surface (48) comprising at least one shoulder (44) having an upper face (43) and a lower face (45). The shoulder has a plurality of passages (42) extending through the shoulder from the upper face (43) to the lower face (45). Each passage (42) is adapted to accommodate a metal coil spring (46) as shown in FIG. 4. The metal coil spring (46) is sized such that it protrudes from each end of the passage (42). In one embodiment, the passages (44) are orientated such that they have a longitudinal axis which is parallel with the longitudinal axis of the tubular shaft (40). The tubular shaft (40) and the shoulder (44) thereon may be constructed from any suitable metallic material including without limit 41/30 alloy steel. The passages (42) may be machined though the shoulder (44).

While the embodiment described herein references the use of metallic compression springs (46) to exert the push force on the bearing elements (30), such description is not intended to be limiting of the invention claimed herein. One skilled in the art will recognize that other suitable types of spring may be used with the apparatus of the present invention.

Assembly and insertion into the bearing assembly (15) of a rotary flow control device (10) will now be described having reference to FIG. 3. Metallic compression springs (46) are loaded into the passages (42) defined by the shoulder (44). Bearing elements (30) are positioned immediately above and below the shoulder (44) such that the bearing elements (30) are in contact with both ends of the springs (46) and such that they compress the spring within the passage (42). Shims (31) are placed above and below the bearing elements (30) as shown in FIG. 3 to further restrain movement of the bearing elements (30). The springs (46) resist compression and exert a preload force on the bearing elements (30). The inner tubular shaft (40) is lowered into the outer housing (22) of the bearing assembly (15). The cap (26) screws into the top of the housing (22) to restrain the inner tubular member (40) and the bearing elements (30) mounted thereon within the outer housing (22).

Specifically, as the inner tubular shaft (40) complete with springs (46), bearings (30) and shims (31) are locked into the outer housing (22) of the bearing assembly (15) of the rotating flow control diverter (10) by tightening and securing the screws (19) of the upper cap (26), the compression of the springs (46) will apply a balanced preload force equally to the bearings (30). This preload force keeps the bearing elements (31) aligned and floating in a neutral position. This reduces the occurrence of friction and excess bearing load arising from misalignment of the bearings or an inability to properly shim the bearings. Springs of varying sizes and compressive resistivity may be selected to vary the spring loaded force exerted on the bearing elements. The passages (42) are placed at regular intervals around the shoulder (44) to promote balanced loading of the adjacent bearing elements (30). The number of passages required is partially dependent on the size and strength of the springs utilized.

The bearing elements may comprise any suitable encased race bearings employed by those skilled in the art in rotating flow control devices.

In one embodiment as shown in FIG. 5, instead of utilizing passages extending through the shoulder, the shoulder defines a series of pockets (50) extending part way through the shoulder, each pocket containing a spring (46) that protrudes out of the opening of the pocket (50). The pockets (50) may be defined on a single face of the shoulder (44), in which case a push force may be exerted on a single bearing element positioned adjacent to the face of the shoulder (44) having the pockets (50). Alternatively pockets (50) may be defined on both faces of the shoulder (44) in which case a push force may be exerted on bearing elements (30) positioned on either side of the shoulder (44) adjacent to the faces of the shoulder (44). The pockets (50) may be machined into the shoulder. In a preferred embodiment, the pockets (50) have a longitudinal axis that is aligned with the longitudinal axis of the tubular shaft (40).

As will be apparent to those skilled in the art, various modifications, adaptations and variations of the foregoing specific disclosure can be made without departing from the scope of the invention claimed herein. 

1. A rotating flow control device apparatus having stabilized bearing elements, the apparatus comprising; (a) a stationary housing having a central bore; (b) a tubular shaft rotatably mounted in the central bore of the stationary housing, the tubular shaft having an inner surface and an outer surface, the outer surface of the tubular shaft defining a shoulder having an upper face and a lower face, the shoulder defining a plurality of passages extending from the upper face to the lower face; (c) a coil spring disposed in each passage; (d) a bearing assembly axially and radially supporting the tubular shaft, the bearing assembly comprising; (i) an outer housing releasably mounted to the stationary housing, the outer housing and the outer surface of the tubular shaft defining an annular space between them; (ii) bearing elements disposed in the annular space, the bearing elements being mounted on the outer surface of the tubular shaft in a position adjacent to the upper and the lower faces of the shoulder whereby the coil springs in the passage are compressed by the bearing elements and exert a resistive push force on the bearing elements.
 2. The apparatus of claim 1 wherein the passages and the tubular shaft are aligned longitudinally.
 3. The apparatus of claim 1 further comprising shims mounted on the outer surface of the tubular shaft adjacent to the bearing elements such that the bearing elements are sandwiched between the shoulder and a shim.
 4. The apparatus of claim 1 further comprising a top cap that releasably attaches to the outer housing of the bearing assembly, the top cap retaining the bearing elements within the annular space and compressing the bearing elements against the springs.
 5. The apparatus of claim 1 wherein the rotating flow control device is a rotating flow control diverter.
 6. The apparatus of claim 1 wherein the rotating flow control device is a rotating blow out preventer.
 7. A rotating flow control device apparatus having a stabilized bearing elements, the apparatus comprising; (a) a stationary housing having a central bore; (b) a tubular shaft rotatably mounted in the central bore of the stationary housing, the tubular shaft having an inner surface and an outer surface, the outer surface of the tubular shaft defining a shoulder having an upper face and a lower face, the shoulder defining a plurality of pockets recessed into the upper face and the lower face; (c) a coil spring disposed in each pocket; (d) a bearing assembly axially and radially supporting the tubular shaft, the bearing assembly comprising; (i) an outer housing releasably mounted to the stationary housing, the outer housing and the outer surface of the tubular shaft defining an annular space between them; (ii) bearing elements disposed in the annular space, the bearing elements being mounted on the outer surface of the tubular shaft in a position adjacent to the upper and the lower faces of the shoulder whereby the coil springs in the pockets are compressed by the bearing elements and exert a resistive push force on the bearing elements.
 8. The apparatus of claim 7 wherein the pockets and the tubular shaft are aligned longitudinally.
 9. The apparatus of claim 7 further comprising shims mounted on the outer surface of the tubular shaft adjacent to the bearing elements such that the bearing elements are sandwiched between the shoulder and the shims.
 10. The apparatus of claim 7 further comprising a top cap that releasably attaches to the outer housing of the bearing assembly, the top cap retaining the bearing elements within the annular space and compressing the bearing elements against the springs.
 11. The apparatus of claim 7 wherein the rotating flow control device is a rotating flow control diverter.
 12. The apparatus of claim 7 wherein the rotating flow control device is a rotating blow out preventer.
 13. The apparatus of claim 7 wherein the pockets are only defined in one of the faces of the shoulder and a single bearing element is mounted on the outer surface of the tubular shaft adjacent to such face.
 14. A method of stabilizing bearing elements in a bearing assembly of a rotating flow control device, the bearing assembly comprising an outer housing, the bearing elements and a rotatable tubular shaft having an outer surface, the tubular shaft being disposed within the outer housing and being supported axially and radially by the bearing elements, the method comprising; (a) defining a shoulder having an upper face and a lower face on the outer surface of the tubular shaft; (b) defining a plurality of passages through the shoulder extending from the upper face to the lower face; (c) inserting a coil spring into each passage; and (d) mounting the bearing elements on the outer surface of the tubular shaft in a position adjacent to the upper and lower faces of the shoulder such that the coil springs in the passages are compressed and exert a resistive push force on the bearing elements.
 15. The method of claim 14 wherein the passages and the tubular shaft are aligned longitudinally.
 16. The method of claim 14 further comprising the step of securing a top cap to the outer housing to retain the bearing elements and to compress the bearing elements against the coil springs.
 17. The method of claim 14 wherein the rotating flow control device is a rotating flow control diverter.
 18. The method of claim 14 wherein the rotating flow control device is a rotating blow out preventer.
 19. The method of claim 14 wherein instead of defining passages in the shoulder, pockets are defined in the upper face and the lower face of the shoulder and coil springs are inserted into each such pocket.
 20. The method of claim 19 wherein pockets are only defined in one of the faces of the shoulder. 